1. The Field of the Invention
The present invention generally relates to optical laser alignment systems and more specifically to an improved target device for use in multiple target laser alignment systems.
2. Technical Background
Highly accurate laser systems have been developed for determining the relative alignment of a target station with respect to a reference point. Such systems incorporate a laser beam to establish a reference line-of-sight between the reference point and the target station. Alignment of the target station is then measured based on placement of the target station relative to the reference line-of-sight. When plural alignments between a single reference point and multiple target points are required, the use of a single target alignment system is impractical because it is time consuming to re-establish a reference line-of-sight at each of the individual target stations. As a result, alignment systems have been developed for accurately measuring the alignment of multiple targets. Multiple target alignment systems have greatly benefitted various types of industrial construction.
The methods and designs of multiple target alignment systems vary in complexity and design. In a typical design, a single laser beam and several target devices are utilized to measure the alignment with a reference line-of-sight. A target device is secured to each of the target stations. Different sites of construction pieces to be aligned are selected as target stations. An example would be the framing components of the fuselage of an airplane or bore holes in an engine block.
In one common design, the target device incorporates a cylindrical tooling tube through which the laser beam is directed. The tooling tube is secured in a target mount which is in turn secured to the target station. The target device further incorporates a beam splitter positioned in the tooling tube which reflects a portion of the laser beam at an angle relative to the reference line-of-sight. The target device incorporates a position sensing detector which receives the reflected portion of the laser beam. Based on where the reflected portion contacts the position sensing detector, the alignment of the target device relative to the reference line-of-sight is determined. In this manner, the target device is able to measure the displacement of the target station relative to the laser beam. The remainder of the laser beam passes onward to another target device which reflects another portion of the beam to determine the alignment of that target device. Thus, the alignment of a plurality of target stations may be determined by using a single reference line-of-sight established by the laser beam.
In mounting the target device to the target station care must be taken to ensure that the target device is positioned perpendicular to the laser beam. To the extent the target device is not perpendicular to the laser beam, the alignment measurement will be inaccurate. This is because the beam proceeds at an improper angle relative to the target device. Thus, when the beam contacts the beam splitter, the reflected portion of the beam is directed along an improper course, and consequently, contacts an inaccurate location on the position sensing detector. Improper angle alignment between the beam and the target device frequently occurs when the target device is placed in a target mount. In practice, an extra preparation step is required to ensure that the target device is indeed perpendicular to the alignment beam. This necessary alignment step is time consuming and introduces a potential for human error into the measurement.
Another concern in using multiple target devices is the ability to pass and return the laser beam through the target device without translating the beam. Returning a laser beam through a target device is a practice used in some laser targeting systems. If the laser beam is translated, then it will no longer provide an accurate reference line-of-sight for other target devices. Accordingly, a target device for use in a multiple target device system must pass and return a laser beam without translation.
Thus, it would be an advancement in the art to provide a see-through target device for multiple target alignment systems which eliminates alignment inaccuracies based on pivotal movement or imperfect mounting of the target device.
It would be a further advancement in the art to provide such a target device for multiple target alignment systems which passes and returns the laser beam without translation.
It would be another advantage advancement in the art to provide such a target device for multiple target alignment systems which is economical to manufacture and accurately operate even by persons having relatively little skill or training.
Such a device is disclosed and claimed herein.